/****************************************************************************
**
**  This file is part of GAP, a system for computational discrete algebra.
**
**  Copyright of GAP belongs to its developers, whose names are too numerous
**  to list here. Please refer to the COPYRIGHT file for details.
**
**  SPDX-License-Identifier: GPL-2.0-or-later
**
**  This file contains  the functions of the  package with the operations for
**  generic lists.
*/

#include "listoper.h"

#include "ariths.h"
#include "bool.h"
#include "calls.h"
#include "error.h"
#include "gvars.h"
#include "io.h"
#include "listfunc.h"
#include "lists.h"
#include "modules.h"
#include "opers.h"
#include "plist.h"
#include "range.h"


#ifndef HPCGAP
// HACK
#define CheckedMakeImmutable(x) MakeImmutable(x)
#endif


/****************************************************************************
**
*F  EqListList(<listL>,<listR>) . . . . . . . . . test if two lists are equal
**
**  'EqListList' returns  'true' if  the  two lists <listL> and  <listR>  are
**  equal and 'false' otherwise.  This is a generic function, which works for
**  all types of lists.
*/
Int             EqListList (
    Obj                 listL,
    Obj                 listR )
{
    Int                 lenL;           // length of the left operand
    Int                 lenR;           // length of the right operand
    Obj                 elmL;           // element of the left operand
    Obj                 elmR;           // element of the right operand
    Int                 i;              // loop variable

    // get the lengths of the lists and compare them
    lenL = LEN_LIST( listL );
    lenR = LEN_LIST( listR );
    if ( lenL != lenR ) {
        return 0;
    }

    // loop over the elements and compare them
    for ( i = 1; i <= lenL; i++ ) {
        elmL = ELMV0_LIST( listL, i );
        elmR = ELMV0_LIST( listR, i );
        if ( elmL == 0 && elmR != 0 ) {
            return 0;
        }
        else if ( elmR == 0 && elmL != 0 ) {
            return 0;
        }
        else if ( ! EQ( elmL, elmR ) ) {
            return 0;
        }
    }

    // no differences found, the lists are equal
    return 1;
}

static Obj FuncEQ_LIST_LIST_DEFAULT(Obj self, Obj listL, Obj listR)
{
    return (EqListList( listL, listR ) ? True : False);
}


/****************************************************************************
**
*F  LtListList(<listL>,<listR>) . . . . . . . . . test if two lists are equal
**
**  'LtListList' returns 'true' if  the list <listL>   is less than the  list
**  <listR> and 'false'  otherwise.  This is a  generic function, which works
**  for all types of lists.
*/
Int             LtListList (
    Obj                 listL,
    Obj                 listR )
{
    Int                 lenL;           // length of the left operand
    Int                 lenR;           // length of the right operand
    Obj                 elmL;           // element of the left operand
    Obj                 elmR;           // element of the right operand
    Int                 i;              // loop variable

    // get the lengths of the lists and compare them
    lenL = LEN_LIST( listL );
    lenR = LEN_LIST( listR );

    // loop over the elements and compare them
    for ( i = 1; i <= lenL && i <= lenR; i++ ) {
        elmL = ELMV0_LIST( listL, i );
        elmR = ELMV0_LIST( listR, i );
        if ( elmL == 0 && elmR != 0 ) {
            return 1;
        }
        else if ( elmR == 0 && elmL != 0 ) {
            return 0;
        }
        else if ( ! EQ( elmL, elmR ) ) {
            return LT( elmL, elmR );
        }
    }

    // reached the end of at least one list
    return (lenL < lenR);
}

static Obj FuncLT_LIST_LIST_DEFAULT(Obj self, Obj listL, Obj listR)
{
    return (LtListList( listL, listR ) ? True : False);
}


/****************************************************************************
**
*F  InList(<objL>,<listR>)  . . . . . . . . . . . . membership test for lists
**
**  'InList' returns a   nonzero value if  <objL>  is a  member of  the  list
**  <listR>, and zero otherwise.
*/
static Int InList(Obj objL, Obj listR)
{
    return Fail != POS_LIST(listR, objL, INTOBJ_INT(0));
}

static Obj FuncIN_LIST_DEFAULT(Obj self, Obj obj, Obj list)
{
    return (InList( obj, list ) ? True : False);
}


/****************************************************************************
**
*F  SumSclList(<listL>,<listR>) . . . . . . . . .  sum of a scalar and a list
*F  SumListScl(<listL>,<listR>) . . . . . . . . .  sum of a list and a scalar
*F  SumListList<listL>,<listR>)  . . . . . . . . . . . . .  sum of two lists
**
**  'SumSclList' is a generic function  for the first kind  of sum, that of a
**  scalar and a list.
**
**  'SumListScl' is a generic function for the second  kind of sum, that of a
**  list and a scalar.
**
**  'SumListList' is a generic  function for the third kind  of sum,  that of
**  two lists.
*/


Obj             SumSclList (
    Obj                 listL,
    Obj                 listR )
{
    Obj                 listS;          // sum, result
    Obj                 elmS;           // one element of sum list
    Obj                 elmR;           // one element of right operand
    Int                 len;            // length
    Int                 i;              // loop variable

    // make the result list
    len = LEN_LIST( listR );
    listS = NEW_PLIST_WITH_MUTABILITY( IS_MUTABLE_OBJ(listL) ||  IS_MUTABLE_OBJ(listR),
                           T_PLIST, len );
    SET_LEN_PLIST( listS, len );

    // loop over the entries and add
    for ( i = 1; i <= len; i++ ) {
        elmR = ELMV0_LIST( listR, i );
        if (elmR)
          {
            elmS = SUM( listL, elmR );
            SET_ELM_PLIST( listS, i, elmS );
            CHANGED_BAG( listS );
          }
    }

    return listS;
}

Obj             SumListScl (
    Obj                 listL,
    Obj                 listR )
{
    Obj                 listS;          // sum, result
    Obj                 elmS;           // one element of sum list
    Obj                 elmL;           // one element of left operand
    Int                 len;            // length
    Int                 i;              // loop variable

    // make the result list
    len = LEN_LIST( listL );
    listS = NEW_PLIST_WITH_MUTABILITY( IS_MUTABLE_OBJ(listR) || IS_MUTABLE_OBJ(listL),
                           T_PLIST, len );
    SET_LEN_PLIST( listS, len );

    // loop over the entries and add
    for ( i = 1; i <= len; i++ ) {
        elmL = ELMV0_LIST( listL, i );
        if (elmL)
          {
            elmS = SUM( elmL, listR );
            SET_ELM_PLIST( listS, i, elmS );
            CHANGED_BAG( listS );
          }
    }

    return listS;
}

Obj             SumListList (
    Obj                 listL,
    Obj                 listR )
{
    Obj                 listS;          // sum, result
    Obj                 elmS;           // one element of the sum
    Obj                 elmL;           // one element of the left list
    Obj                 elmR;           // one element of the right list
    Int                 lenL,lenR, lenS;// lengths
    Int                 i;              // loop variable
    UInt                mutS;

    // get and check the length
    lenL = LEN_LIST( listL );
    lenR = LEN_LIST( listR );
    lenS = (lenR > lenL) ? lenR : lenL;
    listS = NEW_PLIST_WITH_MUTABILITY( IS_MUTABLE_OBJ(listL) || IS_MUTABLE_OBJ(listR),
                           T_PLIST, lenS );
    SET_LEN_PLIST( listS, lenS );

    // Sort out mutability
    mutS = 0;
    for (i = 1; i <= lenL; i++)
      if ((elmL = ELM0_LIST( listL, i)))
        {
          mutS = IS_MUTABLE_OBJ(elmL);
          break;
        }
    for (i = 1; i <= lenR; i++)
      if ((elmR = ELM0_LIST( listR, i)))
        {
          mutS = mutS || IS_MUTABLE_OBJ(elmR);
          break;
        }

    // loop over the entries and add
    for ( i = 1; i <= lenS; i++ ) {
      elmL = ELM0_LIST( listL, i ) ;
      elmR = ELM0_LIST( listR, i ) ;
      elmS =  elmL ? (elmR ? SUM( elmL, elmR ) : mutS ? SHALLOW_COPY_OBJ(elmL): elmL) :
        elmR ? (mutS ? SHALLOW_COPY_OBJ(elmR): elmR) : 0;
      if (elmS)
        {
          SET_ELM_PLIST( listS, i, elmS );
          CHANGED_BAG( listS );
        }
    }

    return listS;
}

static Obj FuncSUM_SCL_LIST_DEFAULT(Obj self, Obj listL, Obj listR)
{
    return SumSclList( listL, listR );
}

static Obj FuncSUM_LIST_SCL_DEFAULT(Obj self, Obj listL, Obj listR)
{
    return SumListScl( listL, listR );
}

static Obj FuncSUM_LIST_LIST_DEFAULT(Obj self, Obj listL, Obj listR)
{
    return SumListList( listL, listR );
}


/****************************************************************************
**
*F  ZeroList(<list>)  . . . . . . . . . . . . . . . . . . . .  zero of a list
*F  ZeroListDefault(<list>) . . . . . . . . . . . . . . . . .  zero of a list
**
**  'ZeroList' is the extended dispatcher for the zero involving lists.  That
**  is, whenever zero for a list is called and 'ZeroSameMutFuncs' does not
**  point to a special function, then 'ZeroList' is called. 'ZeroList'
**  determines the extended type of the operand and then dispatches through
**  'ZeroSameMutFuncs' again.
**
**  'ZeroListDefault' is a generic function for the zero.
*/
static Obj ZeroListDefault(Obj list)
{
    Obj                 res;
// Obj                 elm;
    Int                 len;
    Int                 i;

    // make the result list -- same mutability as argument
    len = LEN_LIST( list );
    if (len == 0) {
        return NEW_PLIST_WITH_MUTABILITY(IS_MUTABLE_OBJ(list), T_PLIST_EMPTY, 0);
    }
    res = NEW_PLIST_WITH_MUTABILITY( IS_MUTABLE_OBJ(list), T_PLIST, len );
    SET_LEN_PLIST( res, len );

    // enter zeroes everywhere
    // For now, lets just do the simplest and safest thing
    for (i = 1; i <= len; i++ )
      {
        Obj tmp = ELM0_LIST( list, i);
        if (tmp) {
          tmp = ZERO_SAMEMUT(tmp);
          SET_ELM_PLIST( res, i,tmp );
          CHANGED_BAG( res);
        }
      }
    // Now adjust the result TNUM info

    if (IS_PLIST( list ))
      {
        if (TNUM_OBJ(list) == T_PLIST_FFE ||
            TNUM_OBJ(list) == T_PLIST_FFE+IMMUTABLE)
          RetypeBag(res, TNUM_OBJ(list));
        else if (TNUM_OBJ(list) >= T_PLIST_CYC &&
                 TNUM_OBJ(list) < T_PLIST_FFE)
          RetypeBagSM(res, T_PLIST_CYC);
        else if (HAS_FILT_LIST(list, FN_IS_DENSE))
          {
            SET_FILT_LIST( res, FN_IS_DENSE );
            if (HAS_FILT_LIST (list, FN_IS_HOMOG))
              {
                SET_FILT_LIST( res, FN_IS_HOMOG);
                if (HAS_FILT_LIST( list, FN_IS_TABLE))
                  {
                    SET_FILT_LIST( res, FN_IS_TABLE);
                    if (HAS_FILT_LIST( list, FN_IS_RECT))
                      SET_FILT_LIST( res, FN_IS_RECT);
                  }
              }
          }
        else if (HAS_FILT_LIST(list, FN_IS_NDENSE))
          SET_FILT_LIST( res, FN_IS_NDENSE );
      }

    return res;
}

static Obj FuncZERO_LIST_DEFAULT(Obj self, Obj list)
{
    return ZeroListDefault( list );
}


static Obj ZeroListMutDefault(Obj list)
{
    Obj                 res;
// Obj                 elm;
    Int                 len;
    Int                 i;

    // make the result list -- always mutable
    len = LEN_LIST( list );
    if (len == 0) {
        return NewEmptyPlist();
    }
    res = NEW_PLIST(  T_PLIST ,len );
    SET_LEN_PLIST( res, len );

    // enter zeroes everywhere
    // For now, lets just do the simplest and safest thing
    for (i = 1; i <= len; i++ )
      {
        Obj tmp = ELM0_LIST( list, i);
        if (tmp) {
          tmp = ZERO_MUT(tmp);
          SET_ELM_PLIST( res, i,tmp );
          CHANGED_BAG( res);
        }
      }
    // Now adjust the result TNUM info

    if (IS_PLIST( list ))
      {
        if (TNUM_OBJ(list) == T_PLIST_FFE ||
            TNUM_OBJ(list) == T_PLIST_FFE+IMMUTABLE)
          RetypeBag(res, T_PLIST_FFE);
        else if (TNUM_OBJ(list) >= T_PLIST_CYC &&
                 TNUM_OBJ(list) < T_PLIST_FFE)
          RetypeBag(res, T_PLIST_CYC);
        else if (HAS_FILT_LIST(list, FN_IS_DENSE))
          {
            SET_FILT_LIST( res, FN_IS_DENSE );
            if (HAS_FILT_LIST (list, FN_IS_HOMOG) &&
                !IS_MUTABLE_OBJ(ELM_PLIST(res,1)))
              {
                SET_FILT_LIST( res, FN_IS_HOMOG);
              }
          }
        else if (HAS_FILT_LIST(list, FN_IS_NDENSE))
          SET_FILT_LIST( res, FN_IS_NDENSE );
      }

    return res;
}

static Obj FuncZERO_MUT_LIST_DEFAULT(Obj self, Obj list)
{
    return ZeroListMutDefault( list );
}



/* This is intended to be installed as a method for the Attribute Zero, for
   rectangular matrices
   rather than the Operation ZeroOp. This is useful because, knowing that
   we want an immutable result, we can (a) reuse a single row of zeros
   (b) record that the result is a rectangular table */

static Obj FuncZERO_ATTR_MAT(Obj self, Obj mat)
{
  Obj zrow;
  UInt len;
  UInt i;
  Obj res;
  len = LEN_LIST(mat);
  if (len == 0)
    return NewImmutableEmptyPlist();
  zrow = ZERO_SAMEMUT(ELM_LIST(mat,1));
  CheckedMakeImmutable(zrow);
  res = NEW_PLIST_IMM(T_PLIST_TAB_RECT, len);
  SET_LEN_PLIST(res,len);
  for (i = 1; i <= len; i++)
    SET_ELM_PLIST(res,i,zrow);
  return res;
}

/****************************************************************************
**
*F  AInvListDefault(<list>) . . . . . . . . . . .  additive inverse of a list
*F  AInvMutListDefault
**
**  'AInvList' is the extended dispatcher for  the additive inverse involving
**  lists.  That is, whenever  the additive inverse for  lists is called  and
**  'AInvSameMutFuncs' does not point to a special function, then 'AInvList'
**  is called.'AInvList' determines the extended type of the operand and then
**  dispatches through 'AInvSameMutFuncs' again.
**
**  'AInvListDefault' is a generic function for the additive inverse.
*/

static Obj AInvMutListDefault(Obj list)
{
    Obj                 res;
    Obj                 elm;
    Int                 len;
    Int                 i;

    /* make the result list -- always mutable, since this might be a method for
       AdditiveInverseOp */
    len = LEN_LIST( list );
    if (len == 0) {
        return NewEmptyPlist();
    }
    res = NEW_PLIST( T_PLIST , len );
    SET_LEN_PLIST( res, len );

    // enter the additive inverses everywhere
    for ( i = 1; i <= len; i++ ) {
        elm = ELM0_LIST( list, i );
        if (elm) {
          elm = AINV_MUT( elm );
          SET_ELM_PLIST( res, i, elm );
          CHANGED_BAG( res );
        }
    }

    // Now adjust the result TNUM info

    if (IS_PLIST(list)) {
        if (TNUM_OBJ(list) == T_PLIST_FFE ||
            TNUM_OBJ(list) == T_PLIST_FFE+IMMUTABLE)
          RetypeBag(res, T_PLIST_FFE);
        else if (TNUM_OBJ(list) >= T_PLIST_CYC &&
                 TNUM_OBJ(list) < T_PLIST_FFE)
          RetypeBag(res, T_PLIST_CYC );
        else if (HAS_FILT_LIST(list, FN_IS_DENSE))
          {
            SET_FILT_LIST( res, FN_IS_DENSE );
            if (HAS_FILT_LIST (list, FN_IS_HOMOG) &&
                !IS_MUTABLE_OBJ(ELM_PLIST(res,1)))
              {
                SET_FILT_LIST( res, FN_IS_HOMOG);

              }
          }
        else if (HAS_FILT_LIST(list, FN_IS_NDENSE))
          SET_FILT_LIST( res, FN_IS_NDENSE );
      }
    return res;
}

static Obj FuncAINV_MUT_LIST_DEFAULT(Obj self, Obj list)
{
    return AInvMutListDefault( list );
}

static Obj AInvListDefault(Obj list)
{
    Obj                 res;
    Obj                 elm;
    Int                 len;
    Int                 i;

    // make the result list -- same mutability as input
    len = LEN_LIST( list );
    if (len == 0) {
        return NEW_PLIST_WITH_MUTABILITY(IS_MUTABLE_OBJ(list), T_PLIST_EMPTY, 0);
    }
    res = NEW_PLIST_WITH_MUTABILITY( IS_MUTABLE_OBJ(list), T_PLIST, len );
    SET_LEN_PLIST( res, len );

    // enter the additive inverses everywhere
    for ( i = 1; i <= len; i++ ) {
        elm = ELM0_LIST( list, i );
        if (elm) {
          elm = AINV_SAMEMUT( elm );
          SET_ELM_PLIST( res, i, elm );
          CHANGED_BAG( res );
        }
    }

    // Now adjust the result TNUM info

    if (IS_PLIST(list)) {
        if (TNUM_OBJ(list) == T_PLIST_FFE ||
            TNUM_OBJ(list) == T_PLIST_FFE+IMMUTABLE)
          RetypeBag(res, TNUM_OBJ(list));
        else if (TNUM_OBJ(list) >= T_PLIST_CYC &&
                 TNUM_OBJ(list) < T_PLIST_FFE)
          RetypeBagSM(res, T_PLIST_CYC);
        else if (HAS_FILT_LIST(list, FN_IS_DENSE))
          {
            SET_FILT_LIST( res, FN_IS_DENSE );
            if (HAS_FILT_LIST (list, FN_IS_HOMOG) &&
                !IS_MUTABLE_OBJ(ELM_PLIST(res,1)))
              {
                SET_FILT_LIST( res, FN_IS_HOMOG);
                if (HAS_FILT_LIST( list, FN_IS_TABLE))
                  {
                    SET_FILT_LIST( res, FN_IS_TABLE);
                    if (HAS_FILT_LIST( list, FN_IS_RECT))
                      SET_FILT_LIST( res, FN_IS_RECT);
                  }
              }
          }
        else if (HAS_FILT_LIST(list, FN_IS_NDENSE))
          SET_FILT_LIST( res, FN_IS_NDENSE );
      }
    return res;
}

static Obj FuncAINV_LIST_DEFAULT(Obj self, Obj list)
{
    return AInvListDefault( list );
}

/****************************************************************************
**
*F  DiffSclList(<listL>,<listR>)  . . . . . difference of a scalar and a list
*F  DiffListScl(<listL>,<listR>)  . . . . . difference of a list and a scalar
*F  DiffListList(<listL>,<listR>) . . . . . . . . . . difference of two lists
**
**  'DiffSclList' is a  generic function  for  the first  kind of difference,
**  that of a scalar and a list.
**
**  'DiffListScl'  is a generic function for the  second kind of  difference,
**  that of a list and a scalar.
**
**  'DiffListList' is  a generic function for the  third  kind of difference,
**  that of two lists.
*/


Obj             DiffSclList (
    Obj                 listL,
    Obj                 listR )
{
    Obj                 listD;          // difference, result
    Obj                 elmD;           // one element of difference list
    Obj                 elmR;           // one element of right operand
    Int                 len;            // length
    Int                 i;              // loop variable
    Int                 mut;

    // make the result list
    len = LEN_LIST( listR );
    mut = IS_MUTABLE_OBJ(listL) || IS_MUTABLE_OBJ(listR);
    if (len == 0) {
        return NEW_PLIST_WITH_MUTABILITY(mut, T_PLIST_EMPTY, 0);
    }
    listD = NEW_PLIST_WITH_MUTABILITY(mut, T_PLIST, len);
    SET_LEN_PLIST( listD, len );

    // loop over the entries and subtract
    for ( i = 1; i <= len; i++ ) {
        elmR = ELMV0_LIST( listR, i );
        if (elmR)
          {
            elmD = DIFF( listL, elmR );
            SET_ELM_PLIST( listD, i, elmD );
            CHANGED_BAG( listD );
          }
    }

    // Now adjust the result TNUM info

    if (IS_PLIST( listR ))
      {
         if (HAS_FILT_LIST(listR, FN_IS_DENSE))
           SET_FILT_LIST( listD, FN_IS_DENSE );
         else if (HAS_FILT_LIST(listR, FN_IS_NDENSE))
           SET_FILT_LIST( listD, FN_IS_NDENSE );
      }
    return listD;
}

Obj             DiffListScl (
    Obj                 listL,
    Obj                 listR )
{
    Obj                 listD;          // difference, result
    Obj                 elmD;           // one element of difference list
    Obj                 elmL;           // one element of left operand
    Int                 len;            // length
    Int                 i;              // loop variable
    Int                 mut;

    // make the result list
    len = LEN_LIST( listL );
    mut = IS_MUTABLE_OBJ(listL) || IS_MUTABLE_OBJ(listR);
    if (len == 0) {
        return NEW_PLIST_WITH_MUTABILITY(mut, T_PLIST_EMPTY, 0);
    }
    listD = NEW_PLIST_WITH_MUTABILITY(mut, T_PLIST, len);
    SET_LEN_PLIST( listD, len );

    // loop over the entries and subtract
    for ( i = 1; i <= len; i++ ) {
        elmL = ELMV0_LIST( listL, i );
        if (elmL)
          {
            elmD = DIFF( elmL, listR );
            SET_ELM_PLIST( listD, i, elmD );
            CHANGED_BAG( listD );
          }

    }

    // Now adjust the result TNUM info

    if (IS_PLIST( listL ))
      {
         if (HAS_FILT_LIST(listL, FN_IS_DENSE))
           SET_FILT_LIST( listD, FN_IS_DENSE );
         else if (HAS_FILT_LIST(listL, FN_IS_NDENSE))
           SET_FILT_LIST( listD, FN_IS_NDENSE );
      }
    return listD;
}

Obj             DiffListList (
    Obj                 listL,
    Obj                 listR )
{
    Obj                 listD;          // difference, result
    Obj                 elmD;           // one element of the difference
    Obj                 elmL;           // one element of the left list
    Obj                 elmR;           // one element of the right list
    Int                 i;              // loop variable
    UInt                mutD;
    Int                 mut;

    // get and check the length
    const UInt lenL = LEN_LIST(listL);
    const UInt lenR = LEN_LIST(listR);
    const UInt lenD = (lenR > lenL) ? lenR : lenL;
    mut = IS_MUTABLE_OBJ(listL) || IS_MUTABLE_OBJ(listR);
    if (lenD == 0) {
        return NEW_PLIST_WITH_MUTABILITY(mut, T_PLIST_EMPTY, 0);
    }
    listD = NEW_PLIST_WITH_MUTABILITY(mut, T_PLIST, lenD);
    SET_LEN_PLIST( listD, lenD );

    // Sort out mutability
    mutD = 0;
    for (i = 1; i <= lenL; i++)
      if ((elmL = ELM0_LIST( listL, i)))
        {
          mutD = IS_MUTABLE_OBJ(elmL);
          break;
        }
    for (i = 1; i <= lenR; i++)
      if ((elmR = ELM0_LIST( listR, i)))
        {
          mutD = mutD || IS_MUTABLE_OBJ(elmR);
          break;
        }


    // loop over the entries and subtract
    for ( i = 1; i <= lenD; i++ ) {
        elmL = ELM0_LIST( listL, i );
        elmR = ELM0_LIST( listR, i );


        // Now compute the result 6 different cases!
        if (elmL)
          {
            if (elmR)
              elmD= DIFF(elmL,elmR);
            else if ( mutD)
              elmD = SHALLOW_COPY_OBJ(elmL);
            else
              elmD = elmL;
          }
        else if (elmR)
          {
            if (mutD)
              elmD = AINV_MUT(elmR);
            else
              elmD = AINV_SAMEMUT(elmR);
          }
        else
          elmD = 0;

        if (elmD)
          {
            SET_ELM_PLIST( listD, i, elmD );
            CHANGED_BAG( listD );
          }
    }
    // Now adjust the result TNUM info. There's not so much we can say
    // here with total reliability

    if (IS_PLIST( listR ) && IS_PLIST(listL) &&
             HAS_FILT_LIST(listR, FN_IS_DENSE) &&
             HAS_FILT_LIST(listL, FN_IS_DENSE))
      SET_FILT_LIST( listD, FN_IS_DENSE );

    return listD;
}

static Obj FuncDIFF_SCL_LIST_DEFAULT(Obj self, Obj listL, Obj listR)
{
    return DiffSclList( listL, listR );
}

static Obj FuncDIFF_LIST_SCL_DEFAULT(Obj self, Obj listL, Obj listR)
{
    return DiffListScl( listL, listR );
}

static Obj FuncDIFF_LIST_LIST_DEFAULT(Obj self, Obj listL, Obj listR)
{
    return DiffListList( listL, listR );
}


/****************************************************************************
**
*F  ProdSclList(<listL>,<listR>)  . . . . . .  product of a scalar and a list
*F  ProdListScl(<listL>,<listR>)  . . . . . .  product of a list and a scalar
*F  ProdListList(<listL>,<listR>) . . . . . . . . . . .  product of two lists
**
**  'ProdSclList' is a generic  function for the first  kind of product, that
**  of a scalar and a list.  Note that this  includes kind of product defines
**  the product of a matrix with a list of matrices.
**
**  'ProdListScl' is a generic function for the  second kind of product, that
**  of a  list  and a  scalar.  Note that   this kind of  product defines the
**  product of a  matrix with a vector, the  product of two matrices, and the
**  product of a list of matrices and a matrix.
**
**  'ProdListList' is a generic function for the third  kind of product, that
**  of two lists.  Note that this kind of product  defines the product of two
**  vectors, a vector and a matrix, and the product of a vector and a list of
**  matrices.
*/

Obj             ProdSclList (
    Obj                 listL,
    Obj                 listR )
{
    Obj                 listP;          // product, result
    Obj                 elmP;           // one element of product list
    Obj                 elmR;           // one element of right operand
    Int                 len;            // length
    Int                 i;              // loop variable
    Int                 mut;

    // make the result list
    len = LEN_LIST( listR );
    mut = IS_MUTABLE_OBJ(listL) || IS_MUTABLE_OBJ(listR);
    if (len == 0) {
        return NEW_PLIST_WITH_MUTABILITY(mut, T_PLIST_EMPTY, 0);
    }
    listP = NEW_PLIST_WITH_MUTABILITY(mut, T_PLIST, len);
    SET_LEN_PLIST( listP, len );

    // loop over the entries and multiply
    for ( i = 1; i <= len; i++ ) {
        elmR = ELMV0_LIST( listR, i );
        if (elmR)
          {
            elmP = PROD( listL, elmR );
            SET_ELM_PLIST( listP, i, elmP );
            CHANGED_BAG( listP );
          }
    }
    if (IS_PLIST( listR ))
      {
         if (HAS_FILT_LIST(listR, FN_IS_DENSE))
           SET_FILT_LIST( listP, FN_IS_DENSE );
         else if (HAS_FILT_LIST(listR, FN_IS_NDENSE))
           SET_FILT_LIST( listP, FN_IS_NDENSE );
      }

    return listP;
}

Obj             ProdListScl (
    Obj                 listL,
    Obj                 listR )
{
    Obj                 listP;          // product, result
    Obj                 elmP;           // one element of product list
    Obj                 elmL;           // one element of left operand
    Int                 len;            // length
    Int                 i;              // loop variable
    Int                 mut;

    // make the result list
    len = LEN_LIST( listL );
    mut = IS_MUTABLE_OBJ(listL) || IS_MUTABLE_OBJ(listR);
    if (len == 0) {
        return NEW_PLIST_WITH_MUTABILITY(mut, T_PLIST_EMPTY, 0);
    }
    listP = NEW_PLIST_WITH_MUTABILITY(mut, T_PLIST, len);
    SET_LEN_PLIST( listP, len );

    // loop over the entries and multiply
    for ( i = 1; i <= len; i++ ) {
        elmL = ELMV0_LIST( listL, i );
        if (elmL) {
          elmP = PROD( elmL, listR );
          SET_ELM_PLIST( listP, i, elmP );
          CHANGED_BAG( listP );
        }
    }

    if (IS_PLIST( listL ))
      {
         if (HAS_FILT_LIST(listL, FN_IS_DENSE))
           SET_FILT_LIST( listP, FN_IS_DENSE );
         else if (HAS_FILT_LIST(listL, FN_IS_NDENSE))
           SET_FILT_LIST( listP, FN_IS_NDENSE );
      }
    return listP;
}

Obj             ProdListList (
    Obj                 listL,
    Obj                 listR )
{
    Obj                 listP;          // product, result
    Obj                 elmP;           // one summand of the product
    Obj                 elmL;           // one element of the left list
    Obj                 elmR;           // one element of the right list
    Int                 lenL,lenR,len; // length
    Int                 i;              // loop variable
    Int                 imm;

    // get and check the length
    lenL = LEN_LIST( listL );
    lenR = LEN_LIST( listR );
    len =  (lenL < lenR) ? lenL : lenR;
    // loop over the entries and multiply and accumulate
    listP = 0;
    imm = 0;
    for (i = 1; i <= len; i++)
      {
        elmL = ELM0_LIST( listL, i );
        elmR = ELM0_LIST( listR, i );
        if (elmL && elmR)
          {
            elmP = PROD( elmL, elmR );
            if (listP)
              listP = SUM( listP, elmP );
            else
              {
                listP = elmP;
                imm = !IS_MUTABLE_OBJ(listP);
              }
          }
    }

    // TODO: This is possible expensive, we may be able to settle for
    // a cheaper check and call MakeImmutable() instead.
    if (imm && IS_MUTABLE_OBJ(listP))
      CheckedMakeImmutable(listP);

    if (!listP)
      ErrorMayQuit("Inner product multiplication of lists: no summands", 0, 0);

    return listP;
}

static Obj FuncPROD_SCL_LIST_DEFAULT(Obj self, Obj listL, Obj listR)
{
    return ProdSclList( listL, listR );
}

static Obj FuncPROD_LIST_SCL_DEFAULT(Obj self, Obj listL, Obj listR)
{
    return ProdListScl( listL, listR );
}

static Obj
FuncPROD_LIST_LIST_DEFAULT(Obj self, Obj listL, Obj listR, Obj depthdiff)
{
  Obj prod;
  prod = ProdListList( listL, listR );

  // possibly adjust mutability
  if (!IS_MUTABLE_OBJ(prod))
    switch (INT_INTOBJ(depthdiff)) {
    case -1:
      if (IS_MUTABLE_OBJ(listL))
        prod = SHALLOW_COPY_OBJ(prod);
      break;
    case 1:
      if (IS_MUTABLE_OBJ(listR))
        prod = SHALLOW_COPY_OBJ(prod);
      break;
    case 0:
      break;
    default:
        ErrorMayQuit("PROD_LIST_LIST_DEFAULT: depth difference should be -1, "
                     "0 or 1, not %d",
                     INT_INTOBJ(depthdiff), 0);
    }
  return prod;

}


/****************************************************************************
**
*F  OneMatrix(<list>, <mut>) . . .  . . . . . . . . . . . . . . one of a list
**
**
**  'OneMatrix' is a generic function for the one. mut may be 0, for an
**  immutable result, 1 for a result of the same mutability level as <list>
**  and 2 for a fully mutable result.
*/

static Obj OneMatrix(Obj mat, UInt mut)
{
    Obj                 res = 0;        // one, result
    Obj                 row;            // one row of the result
    Obj                 zero = 0;       // zero element
    Obj                 one = 0;        // one element
    UInt                len;            // length (and width) of matrix
    UInt                i, k;           // loop variables
    BOOL                rmut;           // rows of result mutable?
    BOOL                cmut;           // result mutable?

    GAP_ASSERT(mut <= 2);

    // check that the operand is a *square* matrix
    len = LEN_LIST( mat );
    if ( len != LEN_LIST( ELM_LIST( mat, 1 ) ) ) {
        ErrorMayQuit("Matrix ONE: <mat> must be square (not %d by %d)",
                     (Int)len, (Int)LEN_LIST(ELM_LIST(mat, 1)));
    }

    // get the zero and the one
    switch (mut) {
    case 0:
      zero = ZERO_MUT( ELM_LIST( ELM_LIST( mat, 1 ), 1 ) );
      one = ONE_SAMEMUT(zero);
      CheckedMakeImmutable(zero);
      CheckedMakeImmutable(one);
      cmut = rmut = FALSE;
      break;

    case 1:
      zero = ZERO_MUT( ELM_LIST( ELM_LIST( mat, 1 ), 1 ) );
      one = ONE_SAMEMUT(zero);
      if (IS_MUTABLE_OBJ(mat))
        {
          cmut = TRUE;
          rmut = IS_MUTABLE_OBJ(ELM_LIST(mat, 1));
        }
      else
          cmut = rmut = FALSE;
      break;

    case 2:
      zero = ZERO_SAMEMUT( ELM_LIST( ELM_LIST( mat, 1 ), 1 ) );
      one  = ONE( zero );
      cmut = rmut = TRUE;
      break;
    }

    // make the identity matrix
    res = NEW_PLIST(T_PLIST, len);
    SET_LEN_PLIST( res, len );
    for ( i = 1; i <= len; i++ ) {
        row = NEW_PLIST(T_PLIST, len);
        SET_LEN_PLIST( row, len );
        for ( k = 1; k <= len; k++ )
            SET_ELM_PLIST( row, k, zero );
        SET_ELM_PLIST( row, i, one );
        if (!rmut)
            MakeImmutableNoRecurse(row);
        SET_ELM_PLIST( res, i, row );
        CHANGED_BAG( res );
    }
    if (!cmut)
        MakeImmutableNoRecurse(res);

    // return the identity matrix
    return res;
}

static Obj FuncONE_MATRIX_IMMUTABLE(Obj self, Obj list)
{
    return OneMatrix( list,0 );
}

static Obj FuncONE_MATRIX_SAME_MUTABILITY(Obj self, Obj list)
{
    return OneMatrix( list,1 );
}

static Obj FuncONE_MATRIX_MUTABLE(Obj self, Obj list)
{
    return OneMatrix( list,2 );
}




/****************************************************************************
**
*F  InvList(<list>) . . . . . . . . . . . . . . . . . . . . inverse of a list
*F  InvMatrix(<list>) . . . . . . . . . . . . . . . . . . . inverse of a list
**
**  'InvList' is the extended dispatcher for  inverses involving lists.  That
**  is, whenever inverse for a list  is called and  'InvFuncs' does not point
**  to  a special function,  then 'InvList'  is called.  'InvList' determines
**  the  extended type of the  operand and then  dispatches through 'InvList'
**  again.
**
**  'InvMatrix' is a generic function for the inverse. In nearly all
**  circumstances, we should use a more efficient function based on
**  calls to AddRowVector, etc.
*/

static Obj InvMatrix(Obj mat, UInt mut)
{
    Obj                 res = 0;        // power, result
    Obj                 row;            // one row of the matrix
    Obj                 row2;           // another row of the matrix
    Obj                 elm;            // one element of the matrix
    Obj                 elm2;           // another element of the matrix
    Obj                 zero = 0;       // zero element
    Obj                 one = 0;        // one element
    UInt                len;            // length (and width) of matrix
    UInt                i, k, l;        // loop variables
    BOOL                rmut;           // rows of result mutable?
    BOOL                cmut;           // result mutable?

    GAP_ASSERT(mut <= 2);

    // check that the operand is a *square* matrix
    len = LEN_LIST( mat );
    if ( len != LEN_LIST( ELM_LIST( mat, 1 ) ) ) {
        ErrorMayQuit("Matrix INV: <mat> must be square (not %d by %d)",
                     (Int)len, (Int)LEN_LIST(ELM_LIST(mat, 1)));
    }

    // get the zero and the one
    switch (mut) {
    case 0:
        zero = ZERO_MUT( ELM_LIST( ELM_LIST( mat, 1 ), 1 ) );
        one = ONE_SAMEMUT(zero);
        CheckedMakeImmutable(zero);
        CheckedMakeImmutable(one);
        cmut = rmut = FALSE;
        break;

    case 1:
        zero = ZERO_MUT( ELM_LIST( ELM_LIST( mat, 1 ), 1 ) );
        one = ONE_SAMEMUT(zero);
        if (IS_MUTABLE_OBJ(mat)) {
            cmut = TRUE;
            rmut = IS_MUTABLE_OBJ(ELM_LIST(mat, 1));
        }
        else
            cmut = rmut = FALSE;
        break;

    case 2:
        zero = ZERO_SAMEMUT( ELM_LIST( ELM_LIST( mat, 1 ), 1 ) );
        one  = ONE( zero );
        cmut = rmut = TRUE;
        break;
    }

    // make a matrix of the form $ ( Id_<len> | <mat> ) $
    res = NEW_PLIST(T_PLIST, len);
    SET_LEN_PLIST(res, len);
    for (i = 1; i <= len; i++) {
        row = NEW_PLIST(T_PLIST, 2 * len);
        SET_LEN_PLIST(row, 2 * len);
        SET_ELM_PLIST(res, i, row);
        CHANGED_BAG(res);
    }
    for ( i = 1; i <= len; i++ ) {
        row = ELM_PLIST( res, i );
        for ( k = 1; k <= len; k++ )
            SET_ELM_PLIST( row, k, zero );
        SET_ELM_PLIST( row, i, one );
    }
    for ( i = 1; i <= len; i++ ) {
        row = ELM_PLIST( res, i );
        row2 = ELM_LIST( mat, i );
        for ( k = 1; k <= len; k++ ) {
            SET_ELM_PLIST( row, k + len, ELM_LIST( row2, k )  );
            CHANGED_BAG( row );
        }
    }

    // make row operations to reach form $ ( <inv> | Id_<len> ) $
    // loop over the columns of <mat>
    for ( k = len+1; k <= 2*len; k++ ) {

        // find a nonzero entry in this column
        for ( i = k-len; i <= len; i++ ) {
            if ( ! EQ( ELM_PLIST( ELM_PLIST(res,i), k ), zero ) )
               break;
        }
        if ( len < i ) {
            return Fail;
        }

        // make the row the <k>-th row and normalize it
        row = ELM_PLIST( res, i );
        SET_ELM_PLIST( res, i, ELM_PLIST( res, k-len ) );
        SET_ELM_PLIST( res, k-len, row );
        if (mut < 2)
          elm2 = INV_SAMEMUT( ELM_PLIST( row, k ) );
        else
          elm2 = INV( ELM_PLIST( row, k ) );
        for ( l = 1; l <= 2*len; l++ ) {
            elm = PROD( elm2, ELM_PLIST( row, l ) );
            SET_ELM_PLIST( row, l, elm );
            CHANGED_BAG( row );
        }

        // clear all entries in this column
        for ( i = 1; i <= len; i++ ) {
            row2 = ELM_PLIST( res, i );
            if (mut < 2)
              elm = AINV_MUT( ELM_PLIST( row2, k ) );
            else
              elm = AINV_SAMEMUT( ELM_PLIST( row2, k ) );
            if ( i != k-len && ! EQ(elm,zero) ) {
                for ( l = 1; l <= 2*len; l++ ) {
                    elm2 = PROD( elm, ELM_PLIST( row, l ) );
                    elm2 = SUM( ELM_PLIST( row2, l ), elm2 );
                    SET_ELM_PLIST( row2, l, elm2 );
                    CHANGED_BAG( row2 );
                }
            }
        }

    }

    // throw away the right halves of each row
    for ( i = 1; i <= len; i++ ) {
        row = ELM_PLIST(res, i);
        SET_LEN_PLIST(row, len);
        SHRINK_PLIST(row, len);
        if (!rmut)
            MakeImmutableNoRecurse(row);
    }
    if (!cmut)
        MakeImmutableNoRecurse(res);

    return res;
}

static Obj FuncINV_MATRIX_MUTABLE(Obj self, Obj mat)
{
  return InvMatrix(mat, 2);
}

static Obj FuncINV_MATRIX_SAME_MUTABILITY(Obj self, Obj mat)
{
  return InvMatrix(mat, 1);
}

static Obj FuncINV_MATRIX_IMMUTABLE(Obj self, Obj mat)
{
  return InvMatrix(mat, 0);
}

/****************************************************************************
**
*F  FuncADD_ROW_VECTOR_5( <self>, <list1>, <list2>, <mult>, <from>, <to> )
**
**  This function adds <mult>*<list2>[i] destructively to <list1>[i] for
**  each i in the range <from>..<to>. It does very little checking
**
*/

// We need these to redispatch when the user has supplied a replacement value.

static Obj AddRowVectorOp;
static Obj MultVectorLeftOp;

static Obj FuncADD_ROW_VECTOR_5(
    Obj self, Obj list1, Obj list2, Obj mult, Obj from, Obj to)
{
    Int ifrom = GetSmallInt("AddRowVector", from);
    Int ito = GetSmallInt("AddRowVector", to);
    if (ito > LEN_LIST(list1) || ito > LEN_LIST(list2))
        ErrorMayQuit("AddRowVector: Upper limit too large", 0, 0);
    for (Int i = ifrom; i <= ito; i++) {
        Obj el1 = ELM_LIST(list1, i);
        Obj el2 = ELM_LIST(list2, i);
        el2 = PROD(mult, el2);
        el1 = SUM(el1, el2);
        ASS_LIST(list1, i, el1);
        CHANGED_BAG(list1);
    }
    return 0;
}

/****************************************************************************
**
*F  FuncADD_ROW_VECTOR_5_FAST(<self>,<list1>,<list2>,<mult>,<from>,<to>)
**
**  This function adds <mult>*<list2>[i] destructively to <list1>[i] for
**  each i in the range <from>..<to>. It does very little checking
**
**  This version is specialised to the "fast" case where list1 and list2 are
**  plain lists of cyclotomics and mult is a small integer.
*/
static Obj FuncADD_ROW_VECTOR_5_FAST(
    Obj self, Obj list1, Obj list2, Obj mult, Obj from, Obj to)
{
    Int ifrom = GetSmallInt("AddRowVector", from);
    Int ito = GetSmallInt("AddRowVector", to);
    if (ito > LEN_LIST(list1) || ito > LEN_LIST(list2))
        ErrorMayQuit("AddRowVector: Upper limit too large", 0, 0);

    Obj prd, sum;
    for (Int i = ifrom; i <= ito; i++) {
        Obj e1 = ELM_PLIST(list1, i);
        Obj e2 = ELM_PLIST(list2, i);
        if (!ARE_INTOBJS(e2, mult) || !PROD_INTOBJS(prd, e2, mult)) {
            prd = PROD(e2, mult);
        }
        if (!ARE_INTOBJS(e1, prd) || !SUM_INTOBJS(sum, e1, prd)) {
            sum = SUM(e1, prd);
            SET_ELM_PLIST(list1, i, sum);
            CHANGED_BAG(list1);
        }
        else
            SET_ELM_PLIST(list1, i, sum);
    }
    return 0;
}

/****************************************************************************
**
*F  FuncADD_ROW_VECTOR_3( <self>, <list1>, <list2>, <mult> )
**
**  This function adds <mult>*<list2>[i] destructively to <list1>[i] for
**  each i in the range 1..Length(<list1>). It does very little checking
**
*T  This could be speeded up still further by using special code for various
**  types of list -- this version just uses generic list ops
*/
static Obj FuncADD_ROW_VECTOR_3(Obj self, Obj list1, Obj list2, Obj mult)
{
  UInt i;
  UInt len = LEN_LIST(list1);
  Obj el1, el2;
  RequireSameLength(SELF_NAME, list1, list2);
  for (i = 1; i <= len; i++)
    {
      el1 = ELMW_LIST(list1,i);
      el2 = ELMW_LIST(list2,i);
      el2 = PROD(mult, el2);
      el1 = SUM(el1 , el2);
      ASS_LIST(list1,i,el1);
      CHANGED_BAG(list1);
    }
  return 0;
}

/****************************************************************************
**
*F  FuncADD_ROW_VECTOR_3_FAST( <self>, <list1>, <list2>, <mult> )
**
**  This function adds <mult>*<list2>[i] destructively to <list1>[i] for
**  each i in the range 1..Length(<list1>). It does very little checking
**
**  This version is specialised to the "fast" case where list1 and list2 are
**  plain lists of cyclotomics and mult is a small integers
*/
static Obj FuncADD_ROW_VECTOR_3_FAST(Obj self, Obj list1, Obj list2, Obj mult)
{
  UInt i;
  Obj e1,e2, prd, sum;
  UInt len = LEN_PLIST(list1);
  RequireSameLength(SELF_NAME, list1, list2);
  for (i = 1; i <= len; i++)
    {
      e1 = ELM_PLIST(list1,i);
      e2 = ELM_PLIST(list2,i);
      if ( !ARE_INTOBJS( e2, mult ) || !PROD_INTOBJS( prd, e2, mult ))
        {
          prd = PROD(e2,mult);
        }
      if ( !ARE_INTOBJS(e1, prd) || !SUM_INTOBJS( sum, e1, prd) )
        {
          sum = SUM(e1,prd);
          SET_ELM_PLIST(list1,i,sum);
          CHANGED_BAG(list1);
        }
      else
          SET_ELM_PLIST(list1,i,sum);
    }
  return 0;
}

/****************************************************************************
**
*F  FuncADD_ROW_VECTOR_2( <self>, <list1>, <list2>)
**
**  This function adds <list2>[i] destructively to <list1>[i] for
**  each i in the range 1..Length(<list1>). It does very little checking
**
*T  This could be speeded up still further by using special code for various
**  types of list -- this version just uses generic list ops
*/
static Obj FuncADD_ROW_VECTOR_2(Obj self, Obj list1, Obj list2)
{
  UInt i;
  Obj el1,el2;
  UInt len = LEN_LIST(list1);
  RequireSameLength(SELF_NAME, list1, list2);
  for (i = 1; i <= len; i++)
    {
      el1 = ELMW_LIST(list1,i);
      el2 = ELMW_LIST(list2,i);
      el1 = SUM(el1, el2 );
      ASS_LIST(list1,i,el1);
      CHANGED_BAG(list1);
    }
  return 0;
}

/****************************************************************************
**
*F  FuncADD_ROW_VECTOR_2_FAST( <self>, <list1>, <list2> )
**
**  This function adds <list2>[i] destructively to <list1>[i] for
**  each i in the range 1..Length(<list1>). It does very little checking
**
**  This version is specialised to the "fast" case where list1 and list2 are
**  plain lists of cyclotomics
*/
static Obj FuncADD_ROW_VECTOR_2_FAST(Obj self, Obj list1, Obj list2)
{
  UInt i;
  Obj e1,e2, sum;
  UInt len = LEN_PLIST(list1);
  RequireSameLength(SELF_NAME, list1, list2);
  for (i = 1; i <= len; i++)
    {
      e1 = ELM_PLIST(list1,i);
      e2 = ELM_PLIST(list2,i);
      if ( !ARE_INTOBJS(e1, e2) || !SUM_INTOBJS( sum, e1, e2) )
        {
          sum = SUM(e1,e2);
          SET_ELM_PLIST(list1,i,sum);
          CHANGED_BAG(list1);
        }
      else
          SET_ELM_PLIST(list1,i,sum);
    }
  return 0;
}

/****************************************************************************
**
*F  MULT_VECTOR_LEFT_RIGHT_2( <list>, <mult>, <left> )
**
**  This function destructively multiplies the entries of <list> by <mult>.
**  It multiplies with <mult> from the left if <left> is not 0 and from the
**  right otherwise.
**  It does very little checking.
**
*/
static inline Obj MULT_VECTOR_LEFT_RIGHT_2(Obj list, Obj mult, UInt left)
{
  UInt i;
  Obj prd;
  UInt len = LEN_LIST(list);
  if (left != 0)
      for (i = 1; i <= len; i++) {
          prd = ELMW_LIST(list, i);
          prd = PROD(mult, prd);
          ASS_LIST(list, i, prd);
          CHANGED_BAG(list);
      }
  else
      for (i = 1; i <= len; i++) {
          prd = ELMW_LIST(list, i);
          prd = PROD(prd, mult);
          ASS_LIST(list, i, prd);
          CHANGED_BAG(list);
      }
  return 0;
}

static Obj FuncMULT_VECTOR_LEFT_2(Obj self, Obj list, Obj mult)
{
    return MULT_VECTOR_LEFT_RIGHT_2(list, mult, 1);
}

static Obj FuncMULT_VECTOR_RIGHT_2(Obj self, Obj list, Obj mult)
{
    return MULT_VECTOR_LEFT_RIGHT_2(list, mult, 0);
}

/****************************************************************************
**
*F  FuncMULT_VECTOR_2_FAST( <self>, <list>, <mult> )
**
**  This function destructively multiplies the entries of <list> by <mult>
**  It does very little checking
**
**  This is the fast method for plain lists of cyclotomics and an integer
**  multiplier
*/

static Obj FuncMULT_VECTOR_2_FAST(Obj self, Obj list, Obj mult)
{
  UInt i;
  Obj el,prd;
  UInt len = LEN_PLIST(list);
  for (i = 1; i <= len; i++)
    {
      el = ELM_PLIST(list,i);
      if (!ARE_INTOBJS(el, mult) || !PROD_INTOBJS(prd,el,mult))
        {
          prd = PROD(el,mult);
          SET_ELM_PLIST(list,i,prd);
          CHANGED_BAG(list);
        }
      else
          SET_ELM_PLIST(list,i,prd);
    }
  return 0;
}

/****************************************************************************
**
*F  FuncPROD_VEC_MAT_DEFAULT( <self>, <vec>, <mat> )
**
**  This is a specialized version of PROD_LIST_LIST_DEFAULT, that uses
**  AddRowVector rather than SUM and PROD.
*/


static Obj FuncPROD_VEC_MAT_DEFAULT(Obj self, Obj vec, Obj mat)
{
  Obj res;
  Obj elt;
  Obj vecr;
  UInt i,len;
  Obj z;
  res = (Obj) 0;
  len = LEN_LIST(vec);
  RequireSameLength("<vec> * <mat>", vec, mat);
  elt = ELMW_LIST(vec,1);
  z = ZERO_SAMEMUT(elt);
  for (i = 1; i <= len; i++)
    {
      elt = ELMW_LIST(vec,i);
      if (!EQ(elt,z))
        {
          vecr = ELMW_LIST(mat,i);
          if (res == (Obj)0)
            {
              res = SHALLOW_COPY_OBJ(vecr);
              CALL_2ARGS(MultVectorLeftOp, res, elt);
            }
          else
            CALL_3ARGS(AddRowVectorOp, res, vecr, elt);
        }
    }
  if (res == (Obj)0)
    res = ZERO_SAMEMUT(ELMW_LIST(mat,1));
  if (!IS_MUTABLE_OBJ(vec) && !IS_MUTABLE_OBJ(mat))
    CheckedMakeImmutable(res);
  return res;
}

/****************************************************************************
**
*F  FuncINV_MAT_DEFAULT
**
**  A faster version of InvMat for those matrices for whose rows AddRowVector
** and MultVectorLeft make sense (and might have fast kernel methods)
**
*/

static Obj ConvertToMatrixRep;

static Obj InvMatWithRowVecs(Obj mat, UInt mut)
{
  Obj                 res;            // result
  Obj                 matcopy;        // copy of mat
  Obj                 row = 0;            // one row of matcopy
  Obj                 row2;           // corresponding row of res
  Obj                 row3;           // another row of matcopy
  Obj                 x = 0;              // one element of the matrix
  Obj                 xi;             // 1/x
  Obj                 y;              // another element of the matrix
  Obj                 yi;             // -y
  Obj                 zero;           // zero element
  Obj                 zerov;          // zero vector
  Obj                 one;            // one element
  UInt                len;            // length (and width) of matrix
  UInt                i, k, j;        // loop variables

  // check that the operand is a *square* matrix
  len = LEN_LIST( mat );
  if ( len != LEN_LIST( ELM_LIST( mat, 1 ) ) ) {
      ErrorMayQuit("Matrix INV: <mat> must be square (not %d by %d)",
                   (Int)len, (Int)LEN_LIST(ELM_LIST(mat, 1)));
  }

  // get the zero and the one
  zerov = ZERO_SAMEMUT(ELMW_LIST(mat, 1));
  zero = ZERO_SAMEMUT(ELMW_LIST(ELMW_LIST(mat, 1), 1));
  one  = ONE( zero );

  // set up res (initially the identity) and matcopy
  res = NEW_PLIST(T_PLIST,len);
  matcopy = NEW_PLIST(T_PLIST,len);
  SET_LEN_PLIST(res,len);
  SET_LEN_PLIST(matcopy,len);
  for (i = 1; i <= len; i++)
    {
      row = SHALLOW_COPY_OBJ(zerov);
      ASS_LIST(row,i,one);
      SET_ELM_PLIST(res,i,row);
      CHANGED_BAG(res);
      row = SHALLOW_COPY_OBJ(ELM_LIST(mat,i));
      SET_ELM_PLIST(matcopy,i,row);
      CHANGED_BAG(matcopy);
    }


  /* Now to work, make matcopy an identity by row operations and
     do the same row operations to res */

  // outer loop over columns of matcopy
  for (i = 1; i <= len; i++)
    {
      // Find a non-zero leading entry that is in that column
      for (j = i; j <= len; j++)
        {
          row = ELM_PLIST(matcopy,j);
          x = ELMW_LIST(row,i);
          if (!EQ(x,zero))
            break;
        }

      // if there isn't one then the matrix is not invertible
      if (j > len)
        return Fail;

      // Maybe swap two rows
      // But I will want this value anyway
      row2 = ELM_PLIST(res,j);
      if (j != i)
        {
          SET_ELM_PLIST(matcopy,j,ELM_PLIST(matcopy,i));
          SET_ELM_PLIST(res,j,ELM_PLIST(res,i));
          SET_ELM_PLIST(matcopy,i,row);
          SET_ELM_PLIST(res,i,row2);
        }

      /*Maybe rescale the row */
      if (!EQ(x, one))
        {
          xi = INV(x);
          CALL_2ARGS(MultVectorLeftOp, row, xi);
          CALL_2ARGS(MultVectorLeftOp, row2, xi);
        }

      // Clear the entries. We know that we can ignore the entries in rows i..j
      for (k = 1; k < i; k++)
        {
          row3 = ELM_PLIST(matcopy,k);
          y = ELMW_LIST(row3,i);
          if (!EQ(y,zero))
            {
              yi = AINV_SAMEMUT(y);
              CALL_3ARGS(AddRowVectorOp, row3, row, yi);
              CALL_3ARGS(AddRowVectorOp, ELM_PLIST(res,k), row2, yi);
            }
        }
      for (k = j+1; k <= len; k++)
        {
          row3 = ELM_PLIST(matcopy,k);
          y = ELMW_LIST(row3,i);
          if (!EQ(y,zero))
            {
              yi = AINV_SAMEMUT(y);
              CALL_3ARGS(AddRowVectorOp, row3, row, yi);
              CALL_3ARGS(AddRowVectorOp, ELM_PLIST(res,k), row2, yi);
            }
        }

    }

  // Now we adjust mutability. Couldn't do it earlier, because AddRowVector,
  // etc. needs mutable target vectors
  switch (mut)
    {
    case 0:
      CheckedMakeImmutable(res);
      break;

    case 1:
      if (IS_MUTABLE_OBJ(mat))
        {
          if (!IS_MUTABLE_OBJ(ELM_LIST(mat,1)))
            for (i = 1; i <= len; i++)
              CheckedMakeImmutable(ELM_LIST(res,i));
        }
      else
        CheckedMakeImmutable(res);
      break;
    case 2:
      break;
    }

  return res;
}


static Obj FuncINV_MAT_DEFAULT_MUTABLE(Obj self, Obj mat)
{
  return InvMatWithRowVecs(mat, 2);
}

static Obj FuncINV_MAT_DEFAULT_SAME_MUTABILITY(Obj self, Obj mat)
{
  return InvMatWithRowVecs(mat, 1);
}

static Obj FuncINV_MAT_DEFAULT_IMMUTABLE(Obj self, Obj mat)
{
  return InvMatWithRowVecs(mat, 0);
}


/****************************************************************************
**
*F  FuncADD_TO_LIST_ENTRIES_PLIST_RANGE( <list>, <range>, <x> )
**
**  This is a method for the operation AddToListEntries, used mainly in
** the MPQS of Stefan Kohl.
**
**  This method requires a plain list for the first argument, and a
**  range for the second and is optimised for the case where x and the list
** entries are small integers, as are their sums
*/

static Obj
FuncADD_TO_LIST_ENTRIES_PLIST_RANGE(Obj self, Obj list, Obj range, Obj x)
{
  UInt low, high, incr;
  Obj y,z;
  UInt i;
  if (!IS_INTOBJ(x))
    return TRY_NEXT_METHOD;
  low = GET_LOW_RANGE(range);
  incr = GET_INC_RANGE(range);
  high = low + incr*(GET_LEN_RANGE(range)-1);
  for (i = low; i <= high; i+= incr)
    {
      y = ELM_PLIST(list,i);
      if (!IS_INTOBJ(y) ||
          !SUM_INTOBJS(z,x,y))
        {
          z = SUM(x,y);
          SET_ELM_PLIST(list,i,z);
          CHANGED_BAG(list);
        }
      else
        SET_ELM_PLIST(list,i,z);

    }
  return (Obj) 0;
}


/****************************************************************************
**
*F  MONOM_TOT_DEG_LEX( u, v ) . . . . . total degree lexicographical ordering
**
**  This function  implements the total degree  plus lexicographical ordering
**  for monomials  of commuting indeterminates.   It is in this  file because
**  monomials  are presently implemented  as lists  of indeterminate-exponent
**  pairs.  Should there be  more functions supporting polynomial arithmetic,
**  then this function should go into a separate file.
**
**  Examples:      x^2y^3 < y^7,   x^4 y^5 < x^3 y^6
*/
static Obj  FuncMONOM_TOT_DEG_LEX ( Obj self, Obj u, Obj  v ) {

  Int4 i, lu, lv;

  Obj  total;
  Obj  lexico;

  if (!IS_PLIST(u) || !IS_DENSE_LIST(u)) {
      RequireArgument(SELF_NAME, u, "must be a dense plain list");
  }
  if (!IS_PLIST(v) || !IS_DENSE_LIST(v)) {
      RequireArgument(SELF_NAME, v, "must be a dense plain list");
  }

  lu = LEN_PLIST( u );
  lv = LEN_PLIST( v );

  // strip off common prefixes
  i = 1;
  while ( i <= lu && i <= lv && EQ(ELM_PLIST( u,i ), ELM_PLIST( v,i )) )
      i++;

  // Is u a prefix of v ? Return true if u is a proper prefix.
  if ( i > lu ) return (lu < lv) ? True : False;

  // Is v a  prefix of u ?
  if ( i > lv ) return False;

  // Now determine the lexicographic order.  The monomial is interpreted
  // as a string of indeterminates.
  if ( i % 2 == 1 ) {
    // The first difference between u and v is an indeterminate.
    lexico = LT(ELM_PLIST( u, i ), ELM_PLIST( v, i )) ? True : False;
    i++;
  }
  else {
    // The first difference between u and v is an exponent.
    lexico = LT(ELM_PLIST( v, i ), ELM_PLIST( u, i )) ? True : False;
  }

  // Now add up the remaining exponents in order to compare the total
  // degrees.
  total = INTOBJ_INT(0);
  while ( i <= lu && i <= lv )  {
    C_SUM_FIA(  total, total, ELM_PLIST( u, i ) );
    C_DIFF_FIA( total, total, ELM_PLIST( v, i ) );
    i += 2;
  }

  // Only one of the following while loops is executed
  while ( i <= lu ) {
    C_SUM_FIA(  total, total, ELM_PLIST( u, i ) );
    i += 2;
  }
  while ( i <= lv ) {
    C_DIFF_FIA( total, total, ELM_PLIST( v, i ) );
    i += 2;
  }

  if ( EQ( total, INTOBJ_INT(0)) ) return lexico;

  return LT( total, INTOBJ_INT(0)) ? True : False;
}

/****************************************************************************
**
*F  MONOM_GRLEX( u, v ) . . . . . ``grlex'' ordering for internal monomials
**
**  This function  implements the ``grlex'' (degree, then lexicographic) ordering
**  for monomials  of commuting indeterminates with x_1>x_2>x_3 etc. (this
**  is standard textbook usage). It is in this  file because
**  monomials  are presently implemented  as lists  of indeterminate-exponent
**  pairs.  Should there be  more functions supporting polynomial arithmetic,
**  then this function should go into a separate file.
**
**  Examples:      x^2y^3 < y^7,   x^4 y^5 < x^3 y^6
*/
static Obj  FuncMONOM_GRLEX( Obj self, Obj u, Obj  v ) {

  Int4 i, lu, lv;

  Obj  total,ai,bi;

  if (!IS_PLIST(u) || !IS_DENSE_LIST(u)) {
      RequireArgument(SELF_NAME, u, "must be a dense plain list");
  }
  if (!IS_PLIST(v) || !IS_DENSE_LIST(v)) {
      RequireArgument(SELF_NAME, v, "must be a dense plain list");
  }

  lu = LEN_PLIST( u );
  lv = LEN_PLIST( v );

  // compare the total degrees
  total = INTOBJ_INT(0);
  for (i=2;i<=lu;i+=2) {
    C_SUM_FIA(  total, total, ELM_PLIST( u, i ) );
  }

  for (i=2;i<=lv;i+=2) {
    C_DIFF_FIA(  total, total, ELM_PLIST( v, i ) );
  }

  if ( ! (EQ( total, INTOBJ_INT(0))) ) {
    // degrees differ, use these
    return LT( total, INTOBJ_INT(0)) ? True : False;
  }

  // now use lexicographic ordering
  i=1;
  while (i<=lu && i<=lv) {
    ai=ELM_PLIST(u,i);
    bi=ELM_PLIST(v,i);
    if (LT(bi,ai)) {
      return True;
    }
    if (LT(ai,bi)) {
      return False;
    }
    ai=ELM_PLIST(u,i+1);
    bi=ELM_PLIST(v,i+1);
    if (LT(ai,bi)) {
      return True;
    }
    if (LT(bi,ai)) {
      return False;
    }
    i+=2;
  }
  if (i<lv) {
      return True;
  }
  return False;
}


/****************************************************************************
**
*F  ZIPPED_SUM_LISTS(z1,z2,zero,f)
**
**  implements the `ZippedSum' function to add polynomials in external
**  representation. This is time critical and thus in the kernel.
**  the function assumes that all lists are plists.
*/
static Obj  FuncZIPPED_SUM_LISTS( Obj self, Obj z1, Obj  z2, Obj zero, Obj f ) {

  Int l1,l2,i;
  Int i1,i2;
  Obj sum,x,y;
  Obj cmpfun,sumfun,a,b,c;

  l1=LEN_LIST(z1);
  l2=LEN_LIST(z2);
  cmpfun=ELM_LIST(f,1);
  sumfun=ELM_LIST(f,2);
  sum=NEW_PLIST(T_PLIST,0);
  i1=1;
  i2=1;
  while ((i1<=l1) && (i2<=l2)) {
// Pr("A= %d %d\n",i1,i2);
    // if z1[i1] = z2[i2] then
    a=ELM_PLIST(z1,i1);
    b=ELM_PLIST(z2,i2);
    if (EQ(a,b)) {
      // the entries are equal
      x=ELM_PLIST(z1,i1+1);
      y=ELM_PLIST(z2,i2+1);
// Pr("EQ, %d %d\n",INT_INTOBJ(x),INT_INTOBJ(y));
      c=CALL_2ARGS(sumfun,x,y);
      if (!(EQ(c,zero))) {
// Pr("Added %d\n",INT_INTOBJ(c), 0);
        AddList(sum,a);
        AddList(sum,c);
      }
      i1=i1+2;
      i2=i2+2;
    }
    else {
      // compare
      a=ELM_PLIST(z1,i1); // in case the EQ triggered a GC
      b=ELM_PLIST(z2,i2);
// Pr("B= %d %d\n",ELM_LIST(a,1),ELM_LIST(b,1));
      c=CALL_2ARGS(cmpfun,a,b);
// Pr("C= %d %d\n",c, 0);

      if ( // this construct is taken from the compiler
          (Obj)(UInt)(c != False) ) {
        a=ELM_PLIST(z1,i1);
        AddList(sum,a);
        c=ELM_PLIST(z1,i1+1);
        AddList(sum,c);
        i1=i1+2;
      }
      else {
        b=ELM_PLIST(z2,i2);
        AddList(sum,b);
        c=ELM_PLIST(z2,i2+1);
        AddList(sum,c);
        i2=i2+2;
      } // else
    } /*else (elif)*/
  } // while

  for (i=i1;i<l1;i+=2) {
    AddList(sum,ELM_PLIST(z1,i));
    AddList(sum,ELM_PLIST(z1,i+1));
  }

  for (i=i2;i<l2;i+=2) {
    AddList(sum,ELM_PLIST(z2,i));
    AddList(sum,ELM_PLIST(z2,i+1));
  }
  return sum;

}

/****************************************************************************
**
*F  FuncMONOM_PROD(m1,m2)
**
**  implements the multiplication of monomials. Both must be plain lists
**  of integers.
*/
static Obj  FuncMONOM_PROD( Obj self, Obj m1, Obj m2 ) {

   UInt a,b,l1,l2,i1,i2,i;
   Obj e,f,c,prod;

   prod=NEW_PLIST(T_PLIST,0);
   l1=LEN_LIST(m1);
   l2=LEN_LIST(m2);
   i1=1;
   i2=1;
   while ((i1<l1) && (i2<l2)) {
     // assume <2^28 variables)
     a=INT_INTOBJ(ELM_PLIST(m1,i1));
     e=ELM_PLIST(m1,i1+1);
     b=INT_INTOBJ(ELM_PLIST(m2,i2));
     f=ELM_PLIST(m2,i2+1);
     if (a==b) {
       C_SUM_FIA(c,e,f); // c=e+f, fast
       AddList(prod,INTOBJ_INT(a));
       AddList(prod,c);
       i1+=2;
       i2+=2;
     }
     else {
       if (a<b) {
         AddList(prod,INTOBJ_INT(a));
         AddList(prod,e);
         i1+=2;
       }
       else {
         AddList(prod,INTOBJ_INT(b));
         AddList(prod,f);
         i2+=2;
       }
     }

   }

  for (i=i1;i<l1;i+=2) {
    AddList(prod,ELM_PLIST(m1,i));
    AddList(prod,ELM_PLIST(m1,i+1));
  }

  for (i=i2;i<l2;i+=2) {
    AddList(prod,ELM_PLIST(m2,i));
    AddList(prod,ELM_PLIST(m2,i+1));
  }
  return prod;

}




/****************************************************************************
**
*F * * * * * * * * * * * * * initialize module * * * * * * * * * * * * * * *
*/


/****************************************************************************
**
*V  GVarFuncs . . . . . . . . . . . . . . . . . . list of functions to export
*/
static StructGVarFunc GVarFuncs[] = {

    GVAR_FUNC_2ARGS(EQ_LIST_LIST_DEFAULT, listL, listR),
    GVAR_FUNC_2ARGS(LT_LIST_LIST_DEFAULT, listL, listR),
    GVAR_FUNC_2ARGS(IN_LIST_DEFAULT, obj, list),
    GVAR_FUNC_2ARGS(SUM_SCL_LIST_DEFAULT, listL, listR),
    GVAR_FUNC_2ARGS(SUM_LIST_SCL_DEFAULT, listL, listR),
    GVAR_FUNC_2ARGS(SUM_LIST_LIST_DEFAULT, listL, listR),
    GVAR_FUNC_1ARGS(ZERO_LIST_DEFAULT, list),
    GVAR_FUNC_1ARGS(ZERO_MUT_LIST_DEFAULT, list),
    GVAR_FUNC_1ARGS(ZERO_ATTR_MAT, mat),
    GVAR_FUNC_1ARGS(AINV_LIST_DEFAULT, list),
    GVAR_FUNC_1ARGS(AINV_MUT_LIST_DEFAULT, list),
    GVAR_FUNC_2ARGS(DIFF_SCL_LIST_DEFAULT, listL, listR),
    GVAR_FUNC_2ARGS(DIFF_LIST_SCL_DEFAULT, listL, listR),
    GVAR_FUNC_2ARGS(DIFF_LIST_LIST_DEFAULT, listL, listR),
    GVAR_FUNC_2ARGS(PROD_SCL_LIST_DEFAULT, listL, listR),
    GVAR_FUNC_2ARGS(PROD_LIST_SCL_DEFAULT, listL, listR),
    GVAR_FUNC_3ARGS(PROD_LIST_LIST_DEFAULT, listL, listR, depthDiff),
    GVAR_FUNC_1ARGS(ONE_MATRIX_MUTABLE, list),
    GVAR_FUNC_1ARGS(ONE_MATRIX_SAME_MUTABILITY, list),
    GVAR_FUNC_1ARGS(ONE_MATRIX_IMMUTABLE, list),
    GVAR_FUNC_1ARGS(INV_MATRIX_MUTABLE, list),
    GVAR_FUNC_1ARGS(INV_MATRIX_SAME_MUTABILITY, list),
    GVAR_FUNC_1ARGS(INV_MATRIX_IMMUTABLE, list),
    GVAR_FUNC_5ARGS(ADD_ROW_VECTOR_5, list1, list2, mult, from, to),
    GVAR_FUNC_5ARGS(ADD_ROW_VECTOR_5_FAST, list1, list2, mult, from, to),
    GVAR_FUNC_3ARGS(ADD_ROW_VECTOR_3, list1, list2, mult),
    GVAR_FUNC_3ARGS(ADD_ROW_VECTOR_3_FAST, list1, list2, mult),
    GVAR_FUNC_2ARGS(ADD_ROW_VECTOR_2, list1, list2),
    GVAR_FUNC_2ARGS(ADD_ROW_VECTOR_2_FAST, list1, list2),
    GVAR_FUNC_2ARGS(MULT_VECTOR_LEFT_2, list, mult),
    GVAR_FUNC_2ARGS(MULT_VECTOR_RIGHT_2, list, mult),
    GVAR_FUNC_2ARGS(MULT_VECTOR_2_FAST, list, mult),
    GVAR_FUNC_2ARGS(PROD_VEC_MAT_DEFAULT, vec, mat),
    GVAR_FUNC_1ARGS(INV_MAT_DEFAULT_MUTABLE, mat),
    GVAR_FUNC_1ARGS(INV_MAT_DEFAULT_SAME_MUTABILITY, mat),
    GVAR_FUNC_1ARGS(INV_MAT_DEFAULT_IMMUTABLE, mat),
    GVAR_FUNC_3ARGS(ADD_TO_LIST_ENTRIES_PLIST_RANGE, list, range, x),
    GVAR_FUNC_2ARGS(MONOM_TOT_DEG_LEX, u, v),
    GVAR_FUNC_2ARGS(MONOM_GRLEX, u, v),
    GVAR_FUNC_4ARGS(ZIPPED_SUM_LISTS, list, list, zero, funclist),
    GVAR_FUNC_2ARGS(MONOM_PROD, monomial, monomial),
    { 0, 0, 0, 0, 0 }

};


/****************************************************************************
**
*F  InitKernel( <module> )  . . . . . . . . initialise kernel data structures
**
*/

static Int InitKernel (
    StructInitInfo *    module )
{
    UInt                t1;             // type of left  operand
    UInt                t2;             // type of right operand

    // init filters and functions
    InitHdlrFuncsFromTable( GVarFuncs );

    InitFopyGVar( "AddRowVector", &AddRowVectorOp );
    InitFopyGVar("MultVectorLeft", &MultVectorLeftOp);
    InitFopyGVar( "ConvertToMatrixRep", &ConvertToMatrixRep );


    // install the generic comparisons
    for ( t1 = FIRST_LIST_TNUM; t1 <= LAST_LIST_TNUM; t1++ ) {
        for ( t2 = FIRST_LIST_TNUM; t2 <= LAST_LIST_TNUM; t2++ ) {
            EqFuncs[ t1 ][ t2 ] = EqListList;
        }
    }
    for ( t1 = FIRST_LIST_TNUM; t1 <= LAST_LIST_TNUM; t1++ ) {
        for ( t2 = FIRST_LIST_TNUM; t2 <= LAST_LIST_TNUM; t2++ ) {
            LtFuncs[ t1 ][ t2 ] = LtListList;
        }
    }
    for ( t1 = FIRST_REAL_TNUM; t1 <= LAST_LIST_TNUM; t1++ ) {
        for ( t2 = FIRST_LIST_TNUM; t2 <= LAST_LIST_TNUM; t2++ ) {
            InFuncs[ t1 ][ t2 ] = InList;
        }
    }

    for (t1 = FIRST_LIST_TNUM; t1 <= LAST_LIST_TNUM; t1 ++ ) {
        ZeroSameMutFuncs[t1] = ZeroListDefault;
        ZeroMutFuncs[t1] = ZeroListMutDefault;
    }

    for (t1 = FIRST_LIST_TNUM; t1 <= LAST_LIST_TNUM; t1 ++ ) {
        AInvSameMutFuncs[t1] = AInvListDefault;
        AInvMutFuncs[t1] = AInvMutListDefault;
    }

    // No kernel installations for One or Inverse any more

    /* Sum. Here we can do list + non-list and non-list + list,
       we have to careful about list+list, though, as it might
       really be list+matrix or matrix+list

       for the T_PLIST_CYC and T_PLIST_FFE cases, we know the nesting
       depth (1) and so we can do the cases of adding them to each
       other and to T_PLIST_TAB objects, which have at least nesting
       depth 2. Some of this will be overwritten in vector.c and
       vecffe.c


       everything else needs to wait until the library */

    for (t1 = FIRST_LIST_TNUM; t1 <= LAST_LIST_TNUM; t1++ ) {
      for (t2 = FIRST_REAL_TNUM; t2 < FIRST_LIST_TNUM; t2++ ) {
        SumFuncs[t1][t2] = SumListScl;
        SumFuncs[t2][t1] = SumSclList;
      }

    }
    for (t1 = T_PLIST_CYC; t1 <= T_PLIST_FFE+IMMUTABLE; t1++) {
      for (t2 = T_PLIST_CYC; t2 <= T_PLIST_FFE+IMMUTABLE; t2++) {
        SumFuncs[t1][t2] = SumListList;
      }
      for (t2 = T_PLIST_TAB; t2 <= T_PLIST_TAB_RECT_SSORT+IMMUTABLE; t2++) {
        SumFuncs[t1][t2] = SumSclList;
        SumFuncs[t2][t1] = SumListScl;
      }
    }

    // Diff is just like Sum

    for (t1 = FIRST_LIST_TNUM; t1 <= LAST_LIST_TNUM; t1++ ) {
      for (t2 = FIRST_REAL_TNUM; t2 < FIRST_LIST_TNUM; t2++ ) {
        DiffFuncs[t1][t2] = DiffListScl;
        DiffFuncs[t2][t1] = DiffSclList;
      }
    }
    for (t1 = T_PLIST_CYC; t1 <= T_PLIST_FFE+IMMUTABLE; t1++) {
      for (t2 = T_PLIST_CYC; t2 <= T_PLIST_FFE+IMMUTABLE; t2++) {
        DiffFuncs[t1][t2] = DiffListList;
      }
      for (t2 = T_PLIST_TAB; t2 <= T_PLIST_TAB_RECT_SSORT+IMMUTABLE; t2++) {
        DiffFuncs[t1][t2] = DiffSclList;
        DiffFuncs[t2][t1] = DiffListScl;
      }
    }

    /* Prod.

    Here we can't do the T_PLIST_TAB cases, in case they are nesting depth three or more
    in which case different rules apply.

    It's also less obvious what happens with the empty list
    */


    for (t1 = FIRST_LIST_TNUM; t1 <= LAST_LIST_TNUM; t1++ ) {
      for (t2 = FIRST_REAL_TNUM; t2 < FIRST_LIST_TNUM; t2++ ) {
        ProdFuncs[t1][t2] = ProdListScl;
        ProdFuncs[t2][t1] = ProdSclList;
      }
    }
    for (t1 = T_PLIST_CYC; t1 <= T_PLIST_FFE+IMMUTABLE; t1++) {
      for (t2 = T_PLIST_CYC; t2 <= T_PLIST_FFE+IMMUTABLE; t2++) {
        ProdFuncs[t1][t2] = ProdListList;
      }
    }


    return 0;
}


/****************************************************************************
**
*F  InitLibrary( <module> ) . . . . . . .  initialise library data structures
*/
static Int InitLibrary (
    StructInitInfo *    module )
{

  // init filters and functions
    InitGVarFuncsFromTable( GVarFuncs );

    return 0;
}


/****************************************************************************
**
*F  InitInfoListOper()  . . . . . . . . . . . . . . . table of init functions
*/
static StructInitInfo module = {
    // init struct using C99 designated initializers; for a full list of
    // fields, please refer to the definition of StructInitInfo
    .type = MODULE_BUILTIN,
    .name = "listoper",
    .initKernel = InitKernel,
    .initLibrary = InitLibrary,
};

StructInitInfo * InitInfoListOper ( void )
{
    return &module;
}
